When a specific process is performed on a target object such as a semiconductor wafer, heat is frequently generated from the target object. To perform a stable process on the target object, the heat is absorbed therefrom by using a cooling liquid, so that the process can be carried out while the temperature of the target object is maintained at a constant temperature. For example, an inspection device for inspecting, e.g., a semiconductor wafer (hereinafter, simply referred to as “wafer”) having a plurality of devices formed thereon is required to perform an inspection while cooling the wafer, because heat is generated from each device of the wafer during the inspection. Further, in order to obtain reliability of the devices in a low and/or a high temperature range, the inspection of the wafer is carried out by the inspection device at a minus temperature and/or at a high temperature of, e.g., 100° C. or thereabout.
Now, a conventional inspection device will be described with reference to FIGS. 3 and 4. As shown in FIG. 3, the inspection device E includes, for example, a loader chamber L for transferring a wafer W; a prober chamber P for inspecting electrical characteristics of the wafer W transferred from the loader chamber L; and a controller (not shown). The inspection device E performs a high temperature inspection and a low temperature inspection of the wafer W under the control of the controller.
As illustrated in FIG. 3, the prober chamber P includes a temperature-controllable wafer chuck 1 for mounting thereon the wafer W in a vertically movable manner; an XY table which moves the wafer chuck 1 in X and Y directions; a probe card 3 disposed above the wafer chuck 1; and a position alignment mechanism 4 which enables a plurality of probes 3A of the probe card 3 to be precisely aligned to a plurality of electrode pads of the wafer W on the wafer chuck 1.
Furthermore, as shown in FIG. 3, a test head T of a tester is detachably placed on a head plate 5 of the prober chamber P, and is electrically connected with the probe card 3 via a performance board (not shown). The temperature of the wafer W on the wafer chuck 1 is set, e.g., within a temperature range from a low temperature to a high temperature, and inspection signals are sent to the probes 3A from the tester via the test head T and the performance board, whereby the electrical characteristics of the wafer W are inspected.
When performing the inspection of the electrical characteristics of the wafer W at the low temperature, the wafer W is cooled down to a specific temperature (e.g., −65° C.) in a low temperature range by a cooling jacket (not shown) embedded in the wafer chuck 1. However, when performing the inspection of the electrical characteristics of the wafer W at a high temperature, the wafer W is heated up to a certain temperature (e.g., several tens of degrees centigrade) in a high temperature range by a heating mechanism such as a heater embedded in the wafer chuck 1. Since heat is generated from the wafer W in both of the cases, a cooling liquid is circulated through the cooling jacket inside the wafer chuck 1 in order to absorb the heat from the wafer W so that the wafer W is maintained at a specific temperature level.
As shown in FIGS. 3 and 4, the conventional wafer chuck 1 is provided with a cooling device 6 which cools the heat from the wafer W during the inspection to thereby keep the temperature of the wafer W to be constant. The cooling device 6 has a first cooling liquid circulation path 62 for circulating the cooling liquid between the wafer chuck 1 and a cooling liquid tank 61; a second cooling liquid circulation path 63 for circulating the cooling liquid 61 from the cooling liquid tank 61 to cool or heat it; a temperature detector 64 for detecting the temperature of the cooling liquid within the cooling liquid tank 61; a temperature controller 65 which operates based on the detection result of the temperature detector 64; a temperature control mechanism 66 driven under the control of the temperature controller 65 to cool or heat the cooling liquid which is circulating through the second cooling liquid circulation path 63; and a heater 67 disposed in the second cooling liquid circulation path 63. A first and a second pump 62A and 63A which serve to circulate the cooling liquid are provided in the first and the second cooling liquid circulation path 62 and 63, respectively.
As shown in FIG. 4, the temperature control mechanism 66 includes a compressor 66A; a heat exchanger 66B; and a coolant circulation path 66C interposed between the compressor 66A and the heat exchanger 66B, for circulating a coolant gas therethrough. The coolant circulation path 66C has an outgoing path made up of branch lines 66D and 66E through which the coolant gas flows from the compressor 66A to the heat exchanger 66B; and an incoming path through which the coolant gas returns back to the compressor 66A from the heat exchanger 66B.
Installed on the first branch line 66D is a heat radiator 66G having a cooling fan 66F, and a first electromagnetic valve 66H and an expansion valve 66I are sequentially provided downstream of the heat radiator 66G. The first electromagnetic valve 66H is operated under the control of the temperature controller 65. The coolant gas highly pressurized by the compressor 66A is cooled down and condensed in the heat radiator 66G by the operation of the cooling fan 66F, and is converted into a cooling liquid. The cooling liquid flows into the heat exchanger 66B via the first electromagnetic valve 66H and the expansion valve 66I while they are opened. Then, the cooling liquid is evaporated in the heat exchanger 66B, cooling the cooling liquid in the second cooling liquid circulation path 63, and returns to the compressor 66A.
Furthermore, a depressurization valve 66J and a second electromagnetic valve 66K are sequentially installed in the second branch line 66E in that order from an upstream toward a downstream. The second electromagnetic valve 66K and the heater 67 are operated under the control of the temperature controller 65. The high-temperature and high-pressure coolant gas provided from the compressor 66A is depressurized by the depressurization valve 66J, and is directed into the heat exchanger 66B via the second electromagnetic valve 66K. In the heat exchanger 66B, the high-temperature gas serves to heat the cooling liquid within the second cooling liquid circulation path 63, and then returns to the compressor 66A. If the heating by the heat exchanger is not enough, the heater 67 is operated to complement the insufficient heat efficiency of the heat exchanger 66B. As described, by using the cooling device 6, the cooling liquid of the cooling liquid tank 61 is controlled to reach a certain inspection temperature.
The conventional cooling device 6 can control the temperature of the cooling liquid in the cooling liquid tank 61 within a range from a low temperature (e.g., −65° C.) to a high temperature (from a temperature lower than a boiling point of the cooling liquid to a temperature of several tens of degrees centigrade) by cooling or heating the cooling liquid flowing in the second cooling liquid circulation path 63 by means of the temperature control mechanism 66. However, it is impossible to use a same cooling liquid for both the low temperature and the high temperature range. More specifically, a cooling liquid that can be used within the low temperature range cannot be used within the high temperature range if the level of the high temperature is higher than or equal to the boiling point (e.g., 85° C.) of the cooling liquid observed at a normal pressure. On the contrary, a cooling liquid that can be used at the high temperature of, e.g., 85° C. cannot be used at a low temperature of, e.g., −65° C., because the viscosity of the cooling device becomes excessively high at that low temperature level.
To cope with the above problem, two cooling devices using different cooling liquids may be used for the low and the high temperature range. In this case, however, the cooling jacket of the water chuck 1 needs to be cleaned whenever the cooling devices are replaced. Alternatively, a single cooling device may be used by changing cooling liquids, but the cooling device, along with the cooling jacket of the wafer chuck 1, needs to be cleaned in such case. Therefore, using two kinds of cooling liquids for the low and the high temperature range is not practical.